Argentaffin and non-argentaffin carcinoid tumorurs of the appendix.

Tumours of the vermiform appendix were studied. The majority proved to be carcinoid tumours of the usual argentaffin-positive type but a substantial minority, generally tumours of minute size, were found to have a somewhat different histological pattern and were argentaffinnegative. Some contained argyrophil granules. The non-argentaffin tumours are considered to form a subgroup of carcinoid tumours.